New acoustic parameter characterizing loading history effects

• Published in: Engineering fracture mechanics 2019-04, Vol.210, p.358-366
• Main Authors: Botvina, L.R., Tyutin, M.R.
• Format: Article
• Language: English
• Subjects: Acoustic emission; Acoustic emission gap; Acoustics; b-value; Cyclic loading; Cyclic loads; Damage; Knee; Load history; Medium carbon steels; Parameters; Residual strength; Stages of fracture; Time dependence
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2018.06.020

•Acoustic emission gap before the fracture is proposed as a new AE parameter.•This parameter increases with the number of preliminary loading cycles.•Fracture stages can be characterized by b-value, number of AE signals and AE gap. A new parameter of acoustic emission (TAE) is proposed, which determines the period of acoustic gap before the final fracture under tension of specimens of low- and medium-carbon steels after preliminary cyclic loading. The beginning of the acoustic gap period TAE corresponds to the achievement of the maximum load. TAE increases with the number of cycles of pre-cycling loading, the fracture magnitude and material strength; as the amplitude of the preliminary cyclic loading increases, it decreases. Values of the bAE and the total number of acoustic signals ΣNAE are estimated and the changes of these characteristics at various tension stages are considered. It is shown that the beginning of the plateau in the time dependence of the total number of acoustic signals is accompanied by a sharp decrease in the bAE-value.